.\"	$OpenBSD: pidfile.3,v 1.7 2013/06/05 03:40:26 tedu Exp $
.\"	$NetBSD: pidfile.3,v 1.2 2001/04/12 22:34:31 sommerfeld Exp $
.\"
.\" Copyright (c) 1999 The NetBSD Foundation, Inc.
.\" All rights reserved.
.\"
.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Jason R. Thorpe.
.\"
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.\" modification, are permitted provided that the following conditions
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.Dd $Mdocdate: June 5 2013 $
.Dt PIDFILE 3
.Os
.Sh NAME
.Nm pidfile
.Nd write a daemon pid file
.Sh SYNOPSIS
.In util.h
.Ft int
.Fn pidfile "const char *basename"
.Sh DESCRIPTION
.Fn pidfile
writes a file containing the process ID of the program to the
.Pa /var/run
directory.
The file name has the form
.Pa /var/run/basename.pid .
If the
.Ar basename
argument is NULL,
.Nm
will determine the program name and use that instead.
.Pp
The pid file can be used as a quick reference if
the process needs to be sent a signal.
When the program exits, the pid file will be removed automatically,
unless the program receives a fatal signal.
.Sh RETURN VALUES
.Fn pidfile
returns 0 on success and -1 on failure.
.Sh SEE ALSO
.Xr atexit 3
.Sh HISTORY
The
.Nm
function call appeared in
.Ox 3.0 .
.Sh CAVEATS
If
.Fn pidfile
is called multiple times with different
.Ar basename ,
only the last pidfile will be removed upon exit.
.Pp
.Fn pidfile
uses
.Fn atexit
to ensure the pidfile is unlinked at program exit.
However, programs that use the
.Fn _exit
function (for example, in signal handlers)
will not trigger this behaviour.
